Most residential thermostats include means for entering a single set point and operate to control their associated heating and/or air conditioning system (hereinafter "furnace") to maintain the set point temperature. Substantial energy savings can be achieved if the set point is lowered during periods when the house is unoccupied or the occupants are sleeping and a form of "set back" thermostat employs a mechanical clock which allows the entry of two set points to be achieved at different periods on a repetitive time cycle.
My co-pending application, Ser. No. 778,376, now U.S. Pat. No. 4,206,872, entitled "Electronic Thermostat" discloses a system including a digital memory capable of storing a lengthy schedule of desired temperatures for times within a repetitive cycle. The memory is continually interrogated by a digital clock to output a signal representative of the desired temperature set point at the time and this temperature is compared to the measured building temperature to control the operation of the furnace. This system allows the provision of relatively complicated time/temperature programs to accommodate to the habits of the building's occupants.
My U.S. Pat. No. 4,172,555 discloses an improved form of multiple set-point electronic thermostat in which the system adaptively determines the rate of temperature change that occurs within the building during operation of the heating/cooling system and energizes the furnace a period of time before a programmed temperature in order to insure that the programmed temperature is attained within the building at the proper time.
These systems represent highly economical energy conserving alternatives to conventional residential thermostats but programming the systems is relatively complicated and may be confusing to a user. Also, an appreciable percentage of the manufacturing cost of these systems is dedicated to programming devices and displays that are required to simplify the programming.
The present invention is directed toward an electronic multiple set-point thermostat employing a low cost form of program entry which is easy to understand and use.